1. Field of the Invention
The invention relates to the field of temperature measurement, and particularly to the temperature measurement of the surface of bodies.
2. Description of the Prior Art
The prior art of the temperature measurement of the surface of bodies can be classified into two types, contacting and non-contacting types, for the measuring of running or stationary bodies, in the temperature range of from ambient to 200.degree. C., by using comparatively small and low cost devices.
FIGS. 2A and 2B show a contacting temperature measurement apparatus which utilizes a bead type thermistor.
As is shown in FIG. 2A, the sensing element 51, composed of a bead type thermistor, is connected to the lead wires 50 and contacted to the measured body. In case of FIG. 2B, the sensing element 51 shown in FIG. 2A is attached to a heat resistant soft plastics member 52 and a heat conducting plate 53 composed of thermally conductive and electrically insulating material is attached to a sensing element and these parts are wrapped around by the polyimide tape 54. The temperature measurement is carried out by conducting heat from the measured body to the sensing element via the heat conducting plate 53. The sensing element in both cases is small in size, about 1 mm, and has good sensitivity. However the element shown in FIGS. 2A and 2B, is not applicable in the case where the measured body or the element is easily damaged by the measurement.
As for the non-contacting type, the sensing elements are placed at a certain distance from the measured body.
Therefore this type of measurement apparatus receives the heat from the measured body via an air gap between the sensing element and the measured body.
These prior apparatuses have the following shortcomings.
As for the contacting type:
The sensing elements should be pressed to the measured body with a certain force to carry out the proper measurement, which may cause damage to the element.
As for the non-contacting type:
1. The thermal responsiveness is hampered by the air gap.
2. The accuracy of the measurement is determined by the size of the air gap, that is, the larger the size the lower the accuracy, and the smaller the size the larger the chance of damage.